1. Field of the Invention
This invention relates to a method for preparing 4-hydroxystyrene, and more particularly for preparing 4-hydroxystyrene by reacting 4-acetoxystyrene with a suitable alcohol in the presence of a catalytic amount of a suitable base.
2. Description of the Prior Art
4-Hydroxystyrene is a well-known compound which is itself useful as a food flavoring substance and as an intermediate in the preparation of polymers and copolymers useful in coatings, electronic applications, ion exchange resins, photoresists, etc.
Although there are several known ways to prepare 4-hydroxystyrene, these known methods are not commercially feasible in the further utilization of the 4-hydroxystyrene. The 4-hydroxystyrene itself is difficult to isolate, since it (1) readily decomposes, (2) is toxic via skin absorption, and (3) readily polymerizes and as a result, those skilled in the art have made numerous attempts to find a method of synthesizing 4-hydroxystyrene in a manner which avoids polymerization and provides the 4-hydroxystrene in a medium which can be utilized to prepare particular derivatives therefrom.
A preparation for 4-hydroxystyrene utilizing 4-acetoxystyrene is reported in a paper entitled "Preparation of Vinyl-phenols and Isopropylphenols", Corson et al., Volume 23, April 1958 J. Oro. Chem. In this preparation, 4-acetoxystyrene is saponified in an aqueous system with a large concentration of a base, KOH, to produce an aqueous solution of the potassium salt of 4-hydroxystyrene which is neutralized with acid to precipitate 4-hydroxystyrene. As indicated above, the procedure is not practical or commercially feasible for production of large quantities of 4-hydroxystyrene because the 4-acetoxystyrene and/or the 4-hydroxystyrene is not very stable and readily polymerizes under the aqueous saponification conditions employed therein, which involve high concentrations of soluble base, resulting in poor yields of 4-hydroxystyrene. A more efficient process for producing 4-hydroxystyrene from 4-acetoxystyrene is desired and needed.
An additional method of preparing 4-hydroxystyrene (also know as paravinylphenol) is described for applications related to perfume compositions, and flavoring for food substances in U.S. Pat. No. 4,316,995 to Pittet et al., issued Feb. 23, 1982.
The instant invention provides a method whereby ready polymerization of the 4-acetoxystyrene and/or the 4-hydroxystyrene in the formation of 4-hydroxystyrene is avoided.